MONDAY, July 8, 2002 (HealthDayNews) -- The government's vaccination strategy to combat a smallpox attack by containment would likely cost thousands more lives more than a wider inoculation effort, according to a new analysis.
The smallpox vaccine is highly effective against the virus, but in a small percentage of people it can cause serious and potentially fatal side effects.
Health officials therefore believe that the risks of a mass immunization campaign outweigh the odds of a bioterrorism attack with smallpox -- at least so far. Instead, the Centers for Disease Control and Prevention has advocated a policy of "ring vaccination" and quarantines to contain the deadly virus, which the World Health Organization declared eradicated in 1980.
In this strategy, smallpox vaccine is given as needed to successively wider circles of people who've come into contact with the infection. Only if this approach fails to stem the outbreak would the government proceed with a mass inoculation plan.
However, the three disease modelers -- Edward Kaplan of Yale University and Lawrence Wein and David Craft of the Massachusetts Institute of Technology -- found that in a hypothetical attack on a city with 10 million inhabitants, mass inoculation is the best strategy for reducing deaths.
Last month, an advisory panel for the CDC recommended immunizing roughly 15,000 emergency workers, hospital staff and other "first responders" likely to encounter the disease early in an attack. Officials now believe that number may ultimately reach 500,000, and the government is making plans for a massive public vaccination effort if needed.
Kaplan, Wein and Craft, who report their calculations this week in the Proceedings of the National Academy of Sciences, assume 1,000 people are initially infected in the attack. If so, ring vaccination followed by mass vaccination four weeks later would lead to about 4,100 more deaths than if mass immunizations occurred at the first signs of disease, they said. Mass vaccination would also trim the life span of the outbreak substantially.
The researchers offered two reasons for the difference. Finding contacts of infected people takes precious time, allowing others to become infected and fall ill before they can receive the inoculation. And in dealing with this congestion, "queues" pile up, further sapping the time-sensitive powers of the vaccine.
The researchers said their computer simulations showed vaccinating 40 percent of the city's residents before an attack would prevent nearly 40,000 deaths compared with a targeted inoculation program.
In the absence of a pre-attack immunization, the researchers argue that "serious consideration" be given to swapping the CDC's current policy of ring vaccination for the mass vaccination plan they modeled.
Dr. Craig Smith, a smallpox expert in Georgia and a member of the Infectious Disease Society of America's bioterrorism work group, said mass vaccinations and ring vaccinations are complementary, not mutually exclusive. "There's huge overlap" between the two approaches, said Smith, who was familiar with the computer model offered by Wein, Craft and Kaplan.
"The crux comes down to whatever you think the risk of an attack will be," said Smith, whose group advised the CDC panel. "We're trying to make a decision on a disease that no longer exists outside of a test tube. That's why you hear all the tap dancing."
Officials at the U.S. Department of Health and Human Services, CDC's parent agency, did not return calls for comment Monday.
What To Do
For more on biological terrorism, visit the Center for Civilian Biodefense Strategies at Johns Hopkins University or the Sabin Vaccine Institute.
To learn about the various bioterror weapons, try the American Medical Association.
